curl/docs/libcurl/opts/CURLOPT_DOH_URL.md
Daniel Stenberg eefcc1bda4
docs: introduce "curldown" for libcurl man page format
curldown is this new file format for libcurl man pages. It is markdown
inspired with differences:

- Each file has a set of leading headers with meta-data
- Supports a small subset of markdown
- Uses .md file extensions for editors/IDE/GitHub to treat them nicely
- Generates man pages very similar to the previous ones
- Generates man pages that still convert nicely to HTML on the website
- Detects and highlights mentions of curl symbols automatically (when
  their man page section is specified)

tools:

- cd2nroff: converts from curldown to nroff man page
- nroff2cd: convert an (old) nroff man page to curldown
- cdall: convert many nroff pages to curldown versions
- cd2cd: verifies and updates a curldown to latest curldown

This setup generates .3 versions of all the curldown versions at build time.

CI:

Since the documentation is now technically markdown in the eyes of many
things, the CI runs many more tests and checks on this documentation,
including proselint, link checkers and tests that make sure we capitalize the
first letter after a period...

Closes #12730
2024-01-23 00:29:02 +01:00

2.5 KiB

c SPDX-License-Identifier Title Section Source See-also
Copyright (C) Daniel Stenberg, <daniel.se>, et al. curl CURLOPT_DOH_URL 3 libcurl
CURLOPT_DNS_CACHE_TIMEOUT (3)
CURLOPT_RESOLVE (3)
CURLOPT_VERBOSE (3)

NAME

CURLOPT_DOH_URL - provide the DNS-over-HTTPS URL

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DOH_URL, char *URL);

DESCRIPTION

Pass in a pointer to a URL for the DoH server to use for name resolving. The parameter should be a char pointer to a null-terminated string which must be a valid and correct HTTPS URL.

libcurl does not validate the syntax or use this variable until the transfer is issued. Even if you set a crazy value here, curl_easy_setopt(3) still returns CURLE_OK.

curl sends POST requests to the given DNS-over-HTTPS URL.

To find the DoH server itself, which might be specified using a name, libcurl uses the default name lookup function. You can bootstrap that by providing the address for the DoH server with CURLOPT_RESOLVE(3).

Disable DoH use again by setting this option to NULL.

INHERIT OPTIONS

DoH lookups use SSL and some SSL settings from your transfer are inherited, like CURLOPT_SSL_CTX_FUNCTION(3).

The hostname and peer certificate verification settings are not inherited but can be controlled separately via CURLOPT_DOH_SSL_VERIFYHOST(3) and CURLOPT_DOH_SSL_VERIFYPEER(3).

A set CURLOPT_OPENSOCKETFUNCTION(3) callback is not inherited.

KNOWN BUGS

Even when DoH is set to be used with this option, there are still some name resolves that are performed without it, using the default name resolver mechanism. This includes name resolves done for CURLOPT_INTERFACE(3), CURLOPT_FTPPORT(3), a proxy type set to CURLPROXY_SOCKS4 or CURLPROXY_SOCKS5 and probably some more.

DEFAULT

NULL - there is no default DoH URL. If this option is not set, libcurl uses the default name resolver.

PROTOCOLS

All

EXAMPLE

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    curl_easy_setopt(curl, CURLOPT_DOH_URL, "https://dns.example.com");
    curl_easy_perform(curl);
  }
}

AVAILABILITY

Added in 7.62.0

RETURN VALUE

Returns CURLE_OK on success or CURLE_OUT_OF_MEMORY if there was insufficient heap space.

Note that curl_easy_setopt(3) does immediately parse the given string so when given a bad DoH URL, libcurl might not detect the problem until it later tries to resolve a name with it.